Electric fuse



t'tttoutetl Nova lid, lil lti ures rarsur 2&11360 ELEJTRIC FUSE Thisinvention relates to electrical cartridge type fuses. Such fuses intheir usual application are used to open a circuit when the currentflowing in the circuit exceeds a normal rating for which the circuit isdesigned.

In the use of electrical equipment it is i'ound that overloads occur,such as when several current consuming devices are simultaneouslystarted, resulting in circuit current values which would be harmful ifcontinued. Time is a factor, however, and for relatively short periodsof time such overload currents do not create any undue heating in thecircuit which would cause faut or be detrimental to either the currentor; lines of the circuits or to equipinstalled in the lines.

is an object of this invention to provide a fuse oi a construction whichwill permit overlocals for short periods of time without destroy ing thefusing element but which will open the circuit readily upon continuedoverload.

It is a further object of this invention to provide a fuse oi plug-typeconstruction which will permit short duration over-loads without resorting to moving parts such as dash pots and springs.

A still further object of the invention is to provide a fuse which iscertain in its capacity to function and which may be easily manufacturedwithout any especially costly elements.

Other and ancillary objects of the invention may appear throughout thedescription, the detail drawing, and the appended claims.

In the drawing,

Figure l is a longitudinal cross section view through a fuse embodyingour invention;

Figure 2 is a transverse section View taken on the lines 2-2 in Figure1; and

Figure 3 is an elevation view partly section, to show conditions withinthe fuse immediately prior to the time when the fuse blows or melts. nFigures 1 and 3 are shown the plug-type idge fuse construction .,hichcomprises an atiug tubular body l constructed of glass,

owing, bottom the body rlcal conducting metal of he; temperature suchbrass (A sealing relationship over the ends of the body portion ill bythe brass, copper, or other conductlug metal ferrules l and i lrespectively. Ferrule construction of this lrind is well known in 5 theelectrical industry and need not be elaborated, upon here with theexception that it is necessary to include a sealing cement or othermaterial at the juncture of the tube and the conduction elements it andit which will prevent moisture within the fuse body from leaking out. Asan alternative construction the caps I construction, not shown, 7 5 iiand it or are sl' gle elements rather than twoeleinent is constructed oflow point such an alloy of lead tin depending upon be current capacitydesired. This fusible elemeat is a small hollow capillary tube, disposedcentrally within the fuse body and closed oil at its upper and lowerjunctions with the fuse caps ii and ill. in order to locate the fuseelement with respect to the caps, punched indentations i8 and it areprovided in the upper and lower caps providing a projection on the innersurface of the cap at which point the fuse element may be hired in placein electrical contact with the caps Mend it sealing the ends oi the fuseelement to. The length of fusible element may be made slightly in excessof the distance between the inner surfaces of caps ii and i2 whenassembled so that a tight fit is produced to hold it in place. Furtherinsurance of retention of this element in position may be had byslightly fusing the ends to the caps by the application of controlledheat at the indentations lb and it after the caps El and are positionedover the ends of the fuse body it.

Two small holes ll and ll are provided in one Wall of the fuse element,one of which is located in the proximity of the lower fuse cap and theother, in the proximity of the upper cap. A small quantity of water isintroduced within e e body to an elevation above the lower fuse elementwith the fuse in a as is required for operation. A method of performingthis operation e to provide a small hole in the body of the or in one ofthe metal caps as at it through the water could be introduced,

which in K subsequently be sealed with a drop or solder -aving a highermelting point than any t A erat which would be experienced in liquidsmay be substituted for -'terial as felt or glass wool.

a I water; however, in the description which follows, certainconsiderations are given which are based on the use of water.

There is a certain amount of capillary action within the bore of thefuse element 15. by tubular construction of the element itself,- whichwill carry water upwardly into the tube. This action may be increasedand the functional effects of the fuse varied by fillingthe interior ofthis element It witha drying agent or such niaover that shown in Figure1 may be permitted in-the' fuse if it is desirable,'or conversely, thisquantity of water may be very slight by locating the elevation of thesmall hole H lower in the ,fuse.

l b'will receive no abnormal heat transferred to it by PR losses, auditwill remain relatively cool. In case of an overload or short circuit,the

temperature of the fuse element l5" will rise rapidly. It will not reachmelting temperature ediately since the water within the tube willvchange state and bedriven off before its femperatu're will greatlyexceed 212 F. As steam vapor is generated'b'y' transfer of heat fromthe.

During periods of normal operating 'current with the fuse placed in theline, the element An excess of water sulating tubular body portion,"fuse caps secured to the ends of the body portion, and a hollow tubularfusible element in electrical association.

and sealed off at its ends with the fuse caps, said fusible elementhaving openings extending throughitswall adjacent to its ends, and asupply of liquid partly'fil'ling said body portion to a. prescribedlevel with respect to the location of one of said openings. I

3. In an electric fuse in combination, an insulating. tubular bodyportion, fuse caps. secured to the ends of the body portion, and ahollow tubu- .-lar fusibleelement centrally located with respect j tothe body portion and in electrical associationv and se'aledofi atits'ends with the fuse caps, said fusible element having openingsextending through its wall adjacent to its ends, and a supply of liquidpartly filling said body portion to a prescribed level with respect tothe location of one of said openings. 4. In an electric fuse incombination, an insulating: tubular body portion, fuse caps secured toand ,in liquid tightrelationship with the ends fuse element to the waterwithintheelement,

the hole, and because of the lower temperature of the shell these vaporswill condense and later the vapors will be driven ofl through theupper I.hole il' until thelevel oi the water drops below tend to fall back intothe lower portion of the a shows acondition resulting when. all of theliquid has been driven off from within the tube to the level Just belowthe lower hole'il and has collected in the form of minutedropletson'the' inner surface of the body H0, at which time thetemperature of the fuse element may go beyond 212 F. and may then: reachthe melting point of the fusible material, thus interrupting. the

' electrical circuit. v I v If the excess current-in the-line should atthis time drop off and in case the fuse does not "blow,- then thedroplets will, with normal agitation, return to the lower portion of thebody'and will In case the overload drops to a normal operatfuse on theoutside of the fuse element. Figure ,of the body portlon, and a hollowtubularfusible element in electrical association at itsends with thefuse caps, said fusible element. having openings extending through itswall adjacent to its ends, and asupply of liquid partly filling-saidbody. portion'to a prescribed level with respect to the location of-oneof said openings.

5. In an electric fuse in combination, an" in sulating tubular bodyportion, fuse caps secured to and in liquid tight relationship with theends of the body portion, and a hollow tubular fusible element inelectrical-association and sealed off at its ends with the fuse caps,said fusible element having openings extending through its wall adjacentto it's ends, anda' supply of liquid partly illi- -lngsaidj body portionto'a prescribed level with respect to the location of one of saidopenings.

6. In an. electric fuse. in combix'iation, an ins'ulating tubularbody-portion, fuse caps in liquid I tight relationship'with' the'ends ofthe body portion, conductingmetal' ferrules securing said fuse caps tosaidbody poition',.anda hollow tubular fusible element in electricalassociation at its ends 'with the fuse caps, said fusible element'havingopenings extendingthrough its wall. adjacent to its ends, and a supplyof liquid partly filling said body portion .to a prescribed level withrespect to the location oi one of said openings.

mitting continued service without interruption.

Certain changesin relative size and in material" may be made to permitoperation atany'given temperature.

The invention is illustrated in a practical but I ends, and asupply ofliquid partly filling said simple form of apparatus which, however, maybe considerably modified so far as details of corn the principles. of.the invention.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent is:

.' 1. In an electric fuse in combination, an insulating'tubular bodyportion, fuse caps secured to the ends of the body portion, and a hollowtubular, fusible element in electrical association at its ends with thefusecaps, said fusible element having openings extending through itswall adja-v cent to its ends, and a supply of liquid partly filling saidbody portion to a prescribed level with respect to the location .of oneof said openings.

2. In an electric fuse in combination, an inelement filled with' glasswool and having-open- I '7. In an electric fuse incomblnation, an insulating tubular bodyportiom-fuse caps-secured. to and in liquid tightrelationship with the ends of the body portion and a hollowtubularfusible element in electrical association at its ends with the fusecaps,.said tubular fusible element having openings extendingthro'ughits'wall adjacent its body portion and carried upwardly into saidtubularfusible element by capillary attraction beyond its level within saidbody portion.

8..In anelectric fuse in combination, an in'- sulating tubular bodyportion, fuse caps secured to the ends of the body portion, and 'ahollow. tubular fusible element in electrical association at its endswith the fuse caps, said tubular fusible ingse'xtending throughits walladjacent its ends, anda supply of liquid partly fllllngsaid body portionand carried upwardly into said tubular the level of the liquid withinsaid body portion.

9. In an electric fuse in combination, an in;

e 41 moo sole-ting tubular body portion, fuse caps of relatively highmelting temperature secured to the oi the body portion, and a hollowtubular fusible element of relatively low melting temperature inelectrical association at its ends with the fuse caps, said tubularfusible element having openings extending through its wall adjacent itsends, and a supply of liquid partly filling said body portion toprescribed level 314th respect to the location of said openings.

i=3. Tin an electric fuse in eoiioleination, an ine sulating tubularbody portion, rinse caps secured l0 element.

MELVILIE F. PETERS. JOHN J. PHILLIPS.

